#!/usr/bin/env python

# -*- coding: utf-8 -*-

from collections import OrderedDict

class LastUpdatedOrderedDict(OrderedDict):

def __init__(self, capacity):

super(LastUpdatedOrderedDict, self).__init__()

self._capacity = capacity

def __setitem__(self, key, value):

containsKey = 1 if key in self else 0

if len(self) - containsKey >= self._capacity:

last = self.popitem(last=False)

print 'remove:', last

if containsKey:

del self[key]

print 'set:', (key, value)

else:

print 'add:', (key, value)

OrderedDict.__setitem__(self, key, value)

# test

d = LastUpdatedOrderedDict(capacity=3)

d['A'] = 100

d['B'] = 200

d['C'] = 300

d['D'] = 400

d['E'] = 500

print d